Correct order of blood cells is (on the basis of number):

The correct option is C RBC>Platelet>WBC
There are 5 millions to 5.5 millions of RBCs in mm${}^{–}$${}^3$ of blood, 6000-8000 of WBCs in mm${}^{–}$${}^3$ of blood and 1,500,00-3,500,00 of platelets. Hence, the correct order is:
RBC>Platelet>WBC